Web tension control for multi-unit printing press



July 23, 1963 D. c. Br-:cHToLD Erm. 3,098,432

WEB TENSION CONTROL FOR MULTI-UNIT PRINTING PRESS Filed Aug. 29, 1961 ATTYS.

l l t l l l l States 31,@98A3'2 Patented `l'uly 23, 1963 3,098,432 WEB TENSON CNTRUL FOR MULTI-UNIT PRNTING PRESS Donald C. Beehtoid, Mountville, and Edward W. Stanley,

Lancaster, Pa., assignors to Armstrong Cork Company,

Lancaster, Pa., a corporation of Pennsylvania Filed Aug. 29, 1961, Ser. No. 134,711 4 Claims. (Cl. 10i-152) The present invention relates generally to rotary printing and with particular reference to a rotary printing press system incorporating a plurality of individual printing units preferably of an off-set gravure type.

More specifically, the invention relates to means for establishing and maintaining a precise web tension in a multi-color gravure printing press. p

In multi-color roto-gravure printing presses, accurate and positive control of web tension throughout the run of the web is mandatory in order to maintain accurate registration of the plurality of printing units, to maintain proper and consistent repeat length of the printed image and to keep the web tracking accurately Ithrough the press, Without adequate tension control, acceptable printing results cannot be achieved regardless of how precise and well conceived the printing units themselves may be. Heretofore, many gravure presses have failed to produce the desired quality of work because of lack of an adequate system of web tension control.

It is accordingly an object of the present invention to provide means whereby the web tension in a multi-color or unit gravure type printing press can be established and maintained so as to produce optimum quality of work by the press.

Another object of the invention is to provide means for such accurate and positive control of web tension in a simple and easily adjustable mechanism, and at a minimum cost.

While the present invention is particularly adaptable to heavy webs such as felt bases to be printed with designs for floor coverings which require and will withstand relatively high tensions, it is not limited in this respect and will have broader application.

Additional objects, features and advantages of the present inventio-n will be more readily apparent from the following detailed description of an embodiment thereof when taken together with the accompanying drawings in which:

FIG. l is a fragmentary plan view of a multi-unit press set-up and illustrating the drive arrangement between various components;

FIG. 2 is a side elevational view of the press set-up of FIG. l;

FIG. 3 is an enlarged sectional view taken on line 3--3' of FlG. 2;

FIG. 4 is an enlarged fragmentary view taken on line 4-4 of FIG. 3; and

FIG. 5 is a fragmentary sectional view of a portion of the mechanism at the infeed end of the press.

Referring now' to the drawings, a typical plant installation for multi-unit gravure press will include in plurality of press units in a production line, each of which is adapted to print one color onto a web or otherwise effect a working operation on the web. In the drawings, two such units are broadly designated A and B and through which the web travels, it being understood that any number of such units may be used according to the number of colors or operations desired.

Each of these press units constitutes in one embodiment of the invention, an offset gravure together with the requisite inking and control mechanism, web guiding mechanism, drying chamber, and other features, which are not sho-wn in detail herein as not being necessary to an understanding of the invention.

The web indicated at 1t) consists of any usual or known type of material but preferably a felt base for floor rugs, and the web is initially drawn from rolls thereof (not shown) on a usual unwind stand or the like and prior to passing into or being threaded through the press unit A which is the first in line, it passes through an infeed tension stand broadly designated 12 and after passing through the last of the press units, such as indicated at B, is then fed into and through an outfeed tension stand generally designated 14 prior to passing through other operations or into rolls for further transportation or storage.

The press units themselves can, of course, vary in construction but as schematically shown in the drawings, are of an off-set gravure type including, in coacting operative relationship, `offset roll 16, engraved roll 18, and impression roll Zit with the web passing in the nip between the olf-set and impression rolls lo and 2o respectively where a printing operation takes place. The web passes over and around idler rolls such as shown at 22 in a readily understandable manner.

As previously pointed out, in order to obtain proper printing of the image with optimum results in the finished product, it is necessary that a proper and uniform web tension be maintained. lt is the function of the infeed and outfeed tension stands 12 and 14 respectively to accomplish this end.

All of the press units such as A and B, and the tension stands 12 and 14 are driven from a common drive motor 24 which in turn drives press line shaft 26v through a speed reduction unit 28. The various cylinders or rolls of the individual press units are operatively interconnected and driven by line shaft 26 through suitable transmissions schematically shown at 30.

The structure and operation of the infeed and outfeed tension stands 12 and 14 are substantially identical with the exception of the frictional characteristics of coverings on the tension rolls therein. rl`he description herein accordingly will be directed solely to one of the stands with a brief discussion of the distinctions therebetween. The tension roll 32 is a steel roll having its trunnions 34 rotatably journalled in bearings 36 in side stands 3S. As will be seen from FlG. 2, the web 1o passes stand 12 around idler roll 40 then over and around tension roll 32 around idler roll 42 in a downward direction thence around a further roll 44, and thence outwardly from the tension stand into the press unit A. Shaft 34 of tension roll 32 is driven from the press line shaft through the speed reducer 28, variable speed drive 46 of a Vernier-type character so that very tine increments of speed variation can be obtained, and thence through speed reducer 4S with the interposition of an air clutch 50 which permits disengagement when desired.

The web l0 is impressed against the driven tension roll 32 by means of individual rubber covered trolleys 52 spaced at intervals across the length of the tension roll. Means are provided to exert pressure downwardly on the trolleys in an adjustable manner. While this can be effected manually, it is desirable, as shown in the drawings, to utilize air or hydraulic means. To this end, a pressure system is shown in FIGS. 3 and 4. The individual trolley wheels `S2 can be of a dead-center type or other suitable construction rotatably mounted on trunnions such as at 54 supported in trunnion forks 56 having connected thereto a piston rod `513 which extends into cylinder 60 and carries on its end a piston `62. A spring `64 is interposed between piston 62 and the bottom of cylinder i649 and biases the piston, piston rod, fork and trunnion in a direction away from the roll 32, the trunnion fork being shown in raised or inoperative position in dotted lines in FIG. 4 at 56a. Support means for the trolley and piston mechanism includes frame cross ties in the nature of channels 68 to which is aixed a bracket 70 having spaced depending ears 72 with vertical slots 74 in the lower ends thereof, The trunnions 54 have extended ends inserted through the slots 74 which not only permit vertical movement of the trunnions but also prevent rotation of the trunnions in any direction except with respect to the travel of the tension rolls. An inlet conduit 76 is attached to a suitable source of pressure supply such as air under pressure, with an adjustment valve 78 therein. This conduit 76 is connected into the piston end of each of the cylinders 60 by fittings such as at 80, and thereby air pressure on the pistons can be adjusted and regulated to govern the downward pressure of the trunnions on the surfaces of the tension rolls. An exhaust conduit 82 having a valve 84 therein is connected into line 76 to exhaust the pressure therefrom.

The mechanism described so far has not been found entirely satisfactory and in order to obtain proper adjusted and constant tension of the material from the infeed to outfeed tension stands throughout the various press units, it has been found necessary to cover the steel tension rolls with frictional materials so selected that the web will not slip on the infeed roll but can slip or creep on the outfeed tension roll when the desired value of web tension is attained, and thereafter a constant uniform web tension is achieved. The slip or creep can be kept to a minimum by proper initial adjustment of the draw transmission which can be very finely adjusted as pointed out above, due to the Vernier-type variable speed transmission unit.

Once set for a given set of conditions, no further change i is required except for infrequent adjustment to compensate for wear of the frictional covering. Referring now to FIGS. 4 and 5, these show respectively outfeed and infeed tension rolls 32a and 32b respectively. The roll 32a has a roll clothing or covering thereover which can consist of cork and is designated as 86 while the roll B2b has a covering 88 which can consist of a rubber and cork composition. With this combination of trolleys for impressing the web onto the roll and the differential in frictional characteristics of the coverings on the infeed and outfeed tension rolls together with the very line speed adjustment, extremely accurate results of printing have been obtained and desired web tensions can be set, and a constant uniform web tension achieved.

The drive for the outfeed tension stand is similar to that of the infeed and includes speed reduction unit 90 driven from shaft 26, then driving variable speed unit 92 similar to unit 46, then through air clutch 94 and transmission 96 to the shaft or trunnion of the outfeed tension roll.

The provision of the air clutches also results in good operating characteristics of the mechanism as for example, when idling the press with the cylinders rotating but the web not feeding then the clutches can be disengaged and the tension stands will stop. lSlack will then enter the web and slippage will occur so that no tension or feeding of the web will ensue.

The variable speed transmission on the infeed tension stand is so adjusted as to insure that the infeed tension roll will transport the web at precisely the same speed as the surface speed of the printing cylinders. The variable speed transmission on the outfeed tension stand is then adjusted to permit the outfeed tension roll to run at a slight overspeed with respect to the surface speed of the printing cylinders. Because of the selected frictional characteristics of the tension roll coverings, no slip will occur on the infeed tension roll but the web tends to slip or creep on the outfeed tension roll to create the desired web tension value.

The provision of a plurality of spaced trolleys rather than a single impression roll eliminates the possibility of causing a roping effect on the travelling web, and also, since they are independently operating, prevents difliculties which might otherwise arise due to misalignment and/ or differentials in pressure across the roll.

The description and details of the present application are adequate for an understanding of the claimed invention. For additional details of the over-all press and incorporation of the present invention therein, reference is made to copending application Serial Number 134,606, filed August 29, 1961, entitled Rotary Printing Press and System, and assigned to 'a common assignee with the present application, the details of which are incorporated herein by reference thereto.

Manifestly many changes in details of construction can be effected without departing from the spirit and scope of the invention as defined in and limited solely by the appended claims.

We claim:

1. In a multi-color gravure printing press having a plu rality of printing units through which a travelling web passes with printing cylinders in each unit adapted to imprint a color on the web, means for establishing and maintaining a precise and constant web tension from the infeed end of the press to the outfeed end, said means including an infeed tension stand positioned immediately before the first printing unit and an outfeed tension stand positioned following the last printing unit, tension rolls rotatably mounted in each said tension stand having the web passing thereover and in driving engagement therewith, variable speed drive means for each said tension roll and so adjustable that speed of the infeed tension roll will transport web at the same speed as the surface speed of the printing cylinders and the speed of the outfeed tension roll is at a slight overspeed with respect to the surface speed of the printing cylinders, means pressing the web against said tension rolls, frictional material coverings on said tension rolls, said coverings have different frictional coefficients such that at the so adjusted speeds of said tension rolls and with selected preset pressure on the web from the pressing means the web will be locked in speed time relationship with the surface speed of the printing cylinders and speed metered with no slippage by the infeed tension roll but can tend to creep or slip on the outfeed tension roll when the desired value of web tension is attained.

2. .A multi-color printing press as claimed in claim 1, wherein the covering on said infeed tension roll has a higher coeicient of friction than that on said outfeed tension roll.

3. A multi-color printing press as claimed in claim 2, the covering on said infeed tension roll comprising a rubber and cork composition and the covering on said outfeed tension roll comprising cork.

4. A multi-color printing press as claimed in claim 1, said means pressing the web against said tension rolls comprising a plurality of individual vertically adjustable rotatably mounted rubber covered trolley wheels at spaced intervals `across the length of said tension rolls.

References Cited in the file of this patent l UNITED STATES PATENTS 1,581,151 Yetter Apr. 20, 1926 1,949,237 Bradner Feb. 27, 1934 2,398,822 Faris et al. Apr. 23, 1946 2,787,954 Gaudet et al. Apr. 9, 1957 2,809,582 Crawford Oct. 15, 1957 2,911,908 Johnson Nov. 10, 1959 

1. IN A MULTI-COLOR GRAVURE PRINTING PRESS HAVING A PLURALITY OF PRINTING UNITS THROUGH WHICH A TRAVELLING WEB PASSES WITH PRINTING CYLINDERS IN EACH UNIT ADAPTED TO IMPRINT A COLOR ON THE WEB, MEANS FOR ESTABLISHING AND MAINTAINING A PRECISE AND CONSTANT WEB TENSION FROM THE INFEED END OF THE PRESS TO THE OUTFEED END, SAID MEANS INCLUDING AN INFEED TENSION STAND POSITIONED IMMEDIATELY BEFORE THE FIRST PRINTING UNIT AND AN OUTFEED TENSION STAND POSITIONED FOLLOWING THE LAST PRINTING UNIT, TENSION ROLLS ROTATABLY MOUNTED IN EACH SAID TENSION STAND HAVING THE WEB PASSING THEREOVER AND IN DRIVING ENGAGEMENT THEREWITH, VARIABLE SPEED DRIVE MEANS FOR EACH SAID TENSION ROLL AND SO ADJUSTABLE THAT SPEED OF THE INFEED TENSION ROLL WILL TRANSPORT WEB AT THE SAME SPEED AS THE SURFACE SPEED OF THE PRINTING CYLINDERS AND THE SPEED OF THE OUTFEED TENSION ROLL IS AT A SLIGHT OVERSPEED WITH RESPECT TO THE SURFACE SPEED OF THE PRINTING CYLINDERS, MEANS PRESSING THE WEB AGAINST SAID TENSION ROLLS, FRICTIONAL MATERIAL COVERINGS ON SAID TENSION ROLLS, SAID COVERINGS HAVE DIFFERENT FRICTIONAL COEFFICIENTS SUCH THAT AT THE SO ADJUSTED SPEEDS OF SAID TENSION ROLLS AND WITH SELECTED PRESET PRESSURE ON THE WEB FROM THE PRESSING MEANS THE WEB WILL BE LOCKED IN SPEED TIME RELATIONSHIP WITH THE SURFACE SPEED OF THE PRINTING CYLINDERS AND SPEED METERED WITH NO SLIPPAGE BY THE INFEED TENSION ROLL BUT CAN TEND TO CREEP OR SLIP ON THE OUTFEED TENSION ROLL WHEN THE DESIRED VALUE OF WEB TENSION IS ATTAINED. 